Introducing Ceramic Capacitors for Use in Factory Automation (FA)

In the area of factory automation (FA*1), the smart factory trend has led to a heightened need for smaller devices, improved reliability and higher heat resistance. While in the area of ceramic capacitors, the commercialization of products that are compatible with a wider capacitance range and that support higher withstanding voltage specifications is being promoted.
Here, we introduce examples of circuits, for power supplies and inverters that are actually used in FA applications, and examples of electrolytic capacitors and film capacitors being replaced with multilayer ceramic capacitors and the main points concerning this replacement.

*1 FA:Factory Automation

Factory Automation Block Diagram

Fig.1 Factory Automation Block Diagram

The above figure shows a general block diagram illustrating factory automation.
FA is made up of PLCs, inverter drivers, AC servomotors, various power supplies, and other devices.

This page provides circuit examples for AC/DC and DC/DC converters, examples of inverter circuits, and examples of power supplies for circuit breakers.

Accordingly, temperature compensation-type (Class 1) capacitors are recommended.
On the other hand, for C7, high capacity is required since high frequency noise components must be removed. For this, high dielectric constant (Class 2) capacitors are recommended.

(2) Primary and secondary coupling capacitors (C2) must be capacitors that have obtained safety standard certification.
AC 500-V and AC 400-V rated products are suitable for supplying power to breakers through high impulse resistance.

Replacing Film Capacitors and Electrolytic Capacitors

Reason behind replacement with Multilayer Ceramic Capacitors

In recent years, switching elements, and in particular, power converters, have become able to support higher frequencies and to be driven at higher temperatures. For reasons such as these, practical applications for increasing efficiency have been promoted, which has led to a higher demand for smaller components that are compatible with high temperatures. Multilayer ceramic capacitors have good impedance characteristics at high frequencies and are compatible with high temperatures. Because of these advantages, replacement with multilayer ceramic capacitors is being promoted even in areas where electrolytic capacitors and film capacitors have been traditionally used.
The following introduces the main points and advantages of replacement and an actual example.

Fig. 6 Rated Voltage and Capacitance Range

Fig. 7 Impedance Frequency Characteristics 10μF

When replacing a film or electrolytic capacitor with a multilayer ceramic capacitor, the capacity does not necessarily have to match. Because MLCCs have extremely outstanding impedance characteristics at high frequencies, they can be used even at capacities lower than that of film or electrolytic capacitors if they are on the high frequency side at around 100 kHz.

The maximum allowable working temperature of multilayer ceramic capacitors is 125°C, which makes them ideal for use in hot environments.
In applications, particularly those such as power converters, where higher efficiency is required, components have been developed to support higher frequencies and are being driven at higher temperatures. Multilayer ceramic capacitors support the downsizing of circuit boards and provide greater freedom in design because of their resistance to high temperatures, which makes them suitable for use in hot environments, and their ability to be mounted closer to heat generating sources. Also, in recent years, attention has been focused on the shift over to multilayer ceramic capacitors because of the trend of using entirely SMD components to reduce mounting costs.
For example, as shown in Fig. 7, when there is a high-temperature, heat-generating source, film capacitors had to be mounted away from the heat-generating source in order to withstand the hot environment. However, by replacing traditional capacitors with multilayer ceramic capacitors, SMD components can now be mounted closer to heat-generating sources.

Fig.8 How Replacement with Multilayer Ceramic Capacitors Works

Main points in replacement with multilayer ceramic capacitors

Case 1: Replacement of a snubber capacitor film capacitor with a multilayer ceramic capacitor
The number of cases where replacement is being promoted in power converters is on the increase.